Propeller feathering control switch



y 1952 R. w. SCHROEDER ET AL 17 PROPELLER FEATHEZRING CONTROL SWITCH Filed Jan. 20, 1948 3 Sheets-Sheet 1 y 1952 R. w. SCHROEDER' ET AL 2,517

PROPELLER FEATHERING CONTROL SWITCH Filed Jan. 20, 1948 3 Sheets-Sheet 2 July 8, 1952 R. w. SCHROEDER ET AL 2,602,517

PROPELLER FEATHERING CONTROL SWITCH 5 Sheets-Sheet 3 Filed Jan. 20, 1948 &

a woe/wives Patented July 8, 1952 PROPELLER FEATHERING CONTROL SWITCH Robert W. Schroeder, Middle River, Charles E.

Loughney, Jr., Towson, and Richard A. Engelhardt, Parkville,'Md., assignors to The Glenn L.:Marti.n Company, Middle River, Md., a corporation of Maryland Application .lanuary 20, 1948, Serial No. 3,288

. I 1 I V This invention relates to an automatic feathering control system for airplane engine propellers, and more particularly tothe switch mechanism that is actuated in responseto the power output of'the engine, which actuates the feathering control upon engine failure.

This invention relates to the subject matter of co-pending application Serial No; 756,768, filed June 24, 1947, now U. S. Patent No. 2,595,345, issued on May 6, 1952.

As described in the co-pending application, in the conventional two-engine airplane, a pilot at take-off is fully occupied withmanipulating several controls from the time he leaves the runway through the take-off period until altitude is reached. If, during the critical period of takeoff, one engine should fail, thepilot must cut that engine and feather the propeller to reduce drag, so that the airplane can continue take-off on one engine and reach altitude where the pilot will have time to investigate the cause of theengine failure and determine the proper action to be taken under the circumstances. The pilot must remember to feather the propeller of the engine that has failed, cut off the fuel booster pump, and cut off the engine to-prevent restarting with a feathered propeller. additional controls that must be operated upon the enginefailure, in addition to the several controls that must 'be manipulated fornormal take-off, it is obviousthat even where an airplane is designed for single enginetake-oif, it may be veryhazardou'swhen one engine fails. There-is theadditional hazard resulting from thehuman element,- in---thatthe best of pilots might erroneously-feather the propeller of the engine that is still delivering power. When he realizes that one engine has failed and that the proper procedure is-to feather the propeller and cut off the engine, it is very easy to inadvertently feather the wrong propeller; The use of the automatic feathering control, including the pressure-operated switch of the present invention, will minimize the hazard during take-off, and relieve the pilot of jmuch'of the confusion resultin from an engine failure.

' v The switch mechanism o'f'this invention is a pa rt of the circuit employed to-detect abona fid'e engine failure, "and transmit a' signal of such engine failure to the feathering control. A described inthe co-p endiri-g application, iti important that the mechanism for detecting a-bona I fide engine-failure must be such that-thesignalis transmitted tothe'feathering control only; after the engine hasbeen brought up--to full-torque output before the loss in ressure in -tlie torque Because of the several 7 Claims. (onto-135.72)

meter circuit, indicating engine failure, takes place. Y

It is an object of this invention to provide a switch mechanism in an automatic feathering control system that will respond to the pressure from the torque meter system to actuate the feathering control device.

It is another object of this invention to provide a switch mechanism that may be inserted in the conventional torque meter circuit to take off from the circuit a signal indicating the power output of the engine.

It is another object of this invention to provide a switch mechanism of simple, rugged construction that will withstand the vibration encountered from being mounted on the engine in the torque meter circuit.

which like numerals refer to like parts.

In the drawings: Figure l is a fragmentary sectional view show- 'ing the location and arrangement of the structure of the present invention.

Figure 2 is a fragmentary sectional view taken on the line 2-2 of Figure:3 through the engine and pressure switch. 7 i V Figure 3 is a plan view of the switch assembly.

Figure 4 is a sectional View of the housing of the switch taken on the line 4-4 ofFigu-re 5 taken on the line 5-5 of Figure 4. 1.

Figure 6 isa plan View of the contact springs and mounting ring. l.

Figure 7 is a sectional view taken on the line l-l'ofFigureG.

Figures 8 and 9 are fragmentary sectional views Figure 5 is a sectional view through the housing of the piston and contact assembly shownunder different conditions of pressure. i

The engine and propeller assembly, shown in Figure 1, is a conventional arrangement offthe engine andthe controllable pitch propeller; The pitch of the propeller maybe varied manually or automatically from flat to full feathered'position, depending upon the requirrnents of the airplane. The pitch control-mechanism 'r'nay either comprise electrical orf-hydraul-ic; components,'or some of each." The internal combus- 3 tion engine I has a forward housing 2 through which the shaft 3 extends. Propeller hub 4 contains either hydraulic or electrical mechanism for controlling the pitch of propeller blades 5. Housing 2 contains a conventional torque meter, including a gear train actuating pistons to generate hydraulic pressure in cylinders 6. Pad 1 on housing 2 affords a mounting for the switch mechanism of this invention, generally indicated as 8, as shown in Figure 2. Pad i is formed with.

a depression 5. Passage I5 conducts oil under pressure from the torque meter mechanism to the chamber formed by depressions. The switch assembly is secured to pad 1 by through bolts I5, as shown in Figure 3. The switch, generally indicated as 8, consists of a housing I I, cap member I2 and cover I3.

The housing II has assembled therein electrical contacts Hi, I5 and I5, which will be more fully described in connection with Figures a to 7. Piston assembly I1 is inserted in body assembly I I before cap member I2 is put in place on body assembly II. spring I8 extends between piston assembly I1 and cap I2to hold the piston assembly in its initial position against lock ring IS. A diaphragm 20 is inserted between cover I3 and cap member I2. Suitable gaskets 2i are placed on each side of diaphragm 25 in the assembly. Gaskets 22 and 23 are placed between parts I2 and II and pad I to aiford a suitable seal. Cap member I2 is formed with a depression 25 in the top to form a chamber on one side of diaphragm 25. Passages 25 and 25 are formed in housing I I to afford a passageway for fluid from chamber 9 to chamber 24. Passages 2! and 28 are in communication with passages 25 and 25 to complete the passageway. Similarly aligned passages. and 30 form a return for fluid to passage 3% which communicates with the engine housing. Passage 32, formed in housing II, pro-= vides a drain for any fluid that may seep past piston assembly I'I into the interior of the switch assembly. Cover member I3 is formed with a recess 33forming, with diaphragm 20, a chamber. Cover I3 is also formed with plugged outlets 34,

35 and 35 in communication with recess 35. Out.

let 35 affords a connection for a pressure line, so that the fluid pressure may be transmitted to someindicating instrument. Plugged'outlets 35 and 35 then afford bleeder outlets for the by draulic system. Pressure is. transmitted from the torque meter system through passage I Lchamher 9 and passages 25, 25, 21 and 28 to chamber 25. .The pressure is transmitted then by diaphragm 20 to the fluid in recess 33 and thence to outlet 35 to an indicator.

Piston assembly I'I consists of a piston 42 having a stem 39secured thereto. Plugs 3i and 38, of any suitable non-conductor, complete the piston assemblyand are cut out .to afford a support for metallic ring 40. Nut 4I completesthe assem-- bly of piston-42 and members 31, 38 and 40. The outside diameter of the assembly formed by members 31,38 and 45- is smooth and continuous. The upper portion of member 3lis flanged to affordsv support for the piston assembly on the inside wall over recess to form therewith an annular chamber. A thin sheet of non-conducting material 52 is placed around the outer-wall of an.-

nular chamber 50. Insulating rings 53, 54, 55 and 56 serve as spacers between metallic conductor rings 5'1, 58 and 59. These rings are stacked inside of sleeve 5| with a snug fit to form a compact assembly. Flanged non-conducting sleeve 60 is assembled on top of sleeve" SI and ring 56. Annular lock nut GI holds the rings and sleeves securely assembled in body II. Flange 62 extends upwardly from the bottom wall of member I I and affords an elongated bearing surface for piston 42. One part of the electrical connector plug is shown at63. Wires 54 extend from plug part 63 through annular chamber 50 to a slot in member 5I through which the wires extend into and are secured to rings 51, 58 and 59. A typical contact ring assembly is shown in Figures 6 and '7. Contacts I4 are shown secured to ring 51 by rivets 55. Contacts I4 are so formed that the ends 55 bear upon and slide upon the inner wall of nonconducting ring 56 and sleeve 65, as the spring is deflected. Springs I4 are so formed that with one 'endsecured to ring 51 and the other end free to slide on member 6!], the center portion 61 is held against the outer periphery of piston assembly I? with a predetermined constant contact pressure. Hole 68 is formed in ring 5'! to facilitate securing the end of wire 64 by soldering.

Figures 8 and 9 are more or less diagrammatic, and are intended to show the operations of the fluid-pressure-actuated switch. Ring 40 is shown of such an axial dimension that when the piston assembly is in the initial position under a condition of no pressure, electrical contact is completed through the ring between contacts I4 and I5. These contacts close the circuit in which they are connected when there is no torque being delivered by the engine as indicated by the low pressure in the torque meter system- As the pressure in the torque meter system builds up, with an increase in torque, piston assembly II moves axially of the switch, compressing spring I8. In the extreme position, or high torque pressure position, the circuit will be completed between contacts I5 and I6 by ring 40. Contacts I5 and I6 correspond to the high-torque switch I8 shown in the above-mentioned ,copending application and, as fully set forth therein, when electrical connection is made therebetween, a circuit is completed to arm the automatic feathering system' so that it will be in condition to operate should the engine fail during takeoff. Similarly, contacts I4 and I5 correspond to low-torque switch I9 of the prior application and, asalso described therein, are adapted, in the event of such an engine failure, to complete a circuitto initiate the automatic feathering operation of the associated propeller. Thus contacts I5 and I6 serve to sense high torque operation of the engine while contacts I4 and I5 serve to sense low-torque operation thereof. Under full power operating conditions of theengine, the circuitwill be maintained through contacts I5 and I6. Should the fluid pressure .in the torque. meter system .drop below a predetermined amount, asgdetermined bythe spring I8, piston assembly Ilwill move down;

wardly and. ring 40 will make contact between' T Itv is .to be.-understood:that certain changes,. al

terations', modifications and substitutions may bemade without departing'from the'spiritiandiscope' of the' appended claims;v

We; claim as our invention:v

.1, In 'aniairplane power: plantv having anflenginei and atorque' meter for generating a fluid pressure. signal proportionate: to the torque out-* put. of the engine; torque sensing apparatus for use its an. automatic propeller feathering system;

comprising an electric switch mech'anism connected to said torque meter and actuated in rein said torque meter, switch contacts insaid housing, a member in said housing mounted on said piston tomove therewith in response to the fluid pressure'in said torque meter; said member coacting with said switch contacts to complete electrical connection therebetween upon said piston being returned to said predetermined position by said return spring upon a' loss of fluid pressure in said torquemeter to indicate a decrease in torque output of said engine below a predeterminedvalue'.

2'. In'anairplane power plant having ,an engine,1torque-sensing apparatus? for use in anlautomatic propeller feathering system comprising a torque meter for generating a fluid pressure signal. proportionateto the torque output of the engine, and an electric switch mechanism con nected to said torque meter and actuated by the fluid pressure generated by said torque meter,

said switch mechanism including a housing mounted on said engine and having a cylinder formed therein in fluid communication with said torque meter, a piston in said cylinder movable between high and low pressure positions in response to variations in pressurein said torque meter, a return spring in said cylinder to restore said piston to its low pressure position upon a decrease in pressure in said torque meter, spaced switch contacts in said housing, and a member in said housing mounted on said piston to move therewith in response to the fluid pressure in said torque meter, said member coacting with said switch contacts to complete electrical connection therebetween upon said piston being returned to the low pressure position by said return spring upon a'loss of fluid pressure in said torque meter to indicate a decrease in torque output of said engine. w

3. In an airplane having an engine, torque sensing apparatus for use in an automatic propeller feathering system comprising a torque meter associated with said engine for generating a fluid pressure signal which varies with the torque output of the engine, an electric switch mechanism connected to said torque meter; said switch mechanism comprising a housing having a cylinder formed therein in fluid communication with said torque meter, a piston in said cylinder moved in response to variations in pressure in said torque meter, a return spring in said cylinder .to restore said piston to a predetermined position upon a decrease in pressure in said torque meter, switch contacts in said housing adjacent said cylinder, a member in said housing mounted on said piston to move therewith in response to the-fluid pressure s'a'i'ditorquei meter,- saidmem b'eri c'oacting: witnsaid switch. contacts to completeelectrical: connection therebetween upon said piston being moved to. said' predetermined position by said return spring upon: aloss of fluid pressure insaidtorque meter to indicate a decreasewin torque output of aidengine'.

L In" arr-airplane having an engine, torque sensing apparatusgfor use in an automatic prop'ell'er feathering system comprising aftorque' meter for generating a fluid pressure-signal proportionate to the torque outputof the engine, an electric:- switch mechanism mounted on said engine: and connected to said torque meter and actuated in response to the fluid pressure signal from said torque meter, said switch mechanism includinga housing having: a cylinder formed therein fluid cominu'iiic'ation' with said torque meter, apiston in said cylinder moved in response to 'variationsin pressure in said torque'meter, a return-spring to restore said piston to a-pr'edetermined position upon-a drop of pressure" in said torq'ue meter, a switch contact support formed by 'aplurality of metal rings surroundingsaid cylinder extendinginwardly of the housing therefrom, spacer rings o'finsulating material positioning said metal rings axially of the-housing;

said metal rings each having mounted thereon a plurality of resilient switch contacts, a member mounted on said piston to-be moved therewith, said member beingof such an axial extent that the contacts of the first-'tworingsare electrically connected in saidpredetermined' position to indicate that'said torque is-b'elow a predetermined value, anduponanincrease in-pressureto" a pre'-' determined value,- said member is moved by said piston to electrically disconnect the contacts of the first tworings" and electrically connect the contacts of the next two rings to indicate high torque output from said engine.

5. In an airplane having an engine, torque sensing apparatus for use in-an automatic propeller feathering system comprising a torque meter associated with said engine for generating a fluid pressure signal proportionate to the torque output of the engine, an electric switch mechanism connected to said torque meter and actuated by the fluid pressure generated by said torque meter. said switch mechanism including a housing having a cylinder formed therein in fluid communication with said torque meter, a piston in said cylinder moved in response to variations in pressure in said torque meter, a return spring in said cylinder to restore said piston to a predetermined position upon a decrease in pressure in said torque meter, spaced switch contacts in said housing, a metal member mounted, on said piston to move therewith in response to the fluid pressure in said torque meter, said member adapted to bridge said contacts to'complete electrical connection between said switch contacts upon said piston being returned to said predetermined position by said return spring upon a loss of fluid pressure in said torque meter to indicate a decrease in torque output of said engine.

6. In an airplane having an engine, torque sensing apparatus for use in an automatic propeller feathering system comprising a torque meter associated with said engine for generating a fluid pressure signal in response to the torque output of the engine, an electric switch mechanism connected to said torque meter for operation thereby; said switch mechanism comprising a housing having a cylinder formed therein in fluid communication with said torque meter, a

piston in said cylinder moved in response to variations in pressure in said torque meter, a return spring in said cylinder to restore said piston to a predetermined position upon a decrease in pressure in said torque meter, switch contacts in said housing, and an annular metallic member in said housing mounted on said piston to move therewith in response to the fluid pressure in said torque'meter, said member interconnecting said switchcontacts'to complete electrical connection therebetween upon said piston being returned to said predetermined position by said return spring upon a loss of fluid pressure in said torque meter to indicate a decrease in torque output of said engine.

'7. In an airplane power plant having an engine and a torque meter associated therewith for.

generating a fluid pressure signal proportionate to the torque output of the engine; torque sensing apparatus for use in an automatic propeller feathering system, comprising a switch mechanism connected to said torque meter and actuated in response to the fluid pressure signal from said torque meter, said switch mechanism including a housing having a cylinder formed therein in fluid communication with said torque meter, a piston in said cylinder moved in response to variations in pressure in said torque meter, a return spring to restore said piston to a predetermined position upon a drop of pressure in said torque meter, a switch contact support formed by a plurality of metal rings surrounding said cylinder extending inwardly of the housing therefrom, spacer rings of insulating material positioning said metalrings axially of the housing, said metal rings each having mounted thereon a plurality of resilient switch contacts, an annular member of conducting material mounted on said piston to be moved therewith of such an axial extent that the contacts of the first two rings are electrically connected thereby in said predetermined position, and upon operation of the engine causing an increase in pressure in the torque meter, said memberis moved by said piston to electrically disconnect the contacts of the first two rings, and upon a decrease in torque meter pressure, saidv member is moved by the return,

spring to again close said electrical contacts of said first two rings to indicate a decrease in torque output of the engine.

ROBERT W. SCI-IROEDER. CHARLES E. LOUGHNEY, JR. RICHARD A. ENGELHARDT.

REFERENCES CITED,

The following references are of'record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Publication, Aviation Maintenance and Operations, December 1947, pp, 30 and 31. 

